The present invention relates to an improved joint structure of a take-down type archery bow, and more specifically relates to an improvement in construction of a joint structure of an archery bow in which limbs are joined to a handle riser by means of a two position support.
A take-down bow is in general comprised of a handle riser having sockets at distal ends and a pair of limbs each having a plug to be inserted and held firmly in one of the sockets of the handle riser by means of a two position support. Limbs are formed by plastic moulding of fiber reinforced plastics and core materials and, even having same particulars of design, their dimension and/or configuration vary from limb to limb because of inevitable moulding error. When such limbs with variation are coupled to a handle riser to form an archery bow, the bow naturally has an asymmetric construction which tends to seriously disburb balance of force when the string is drawn for shooting. Such unbalanced distribution of force disenables correct shooting of targets and seriously degrades durability of the elements composing the archery bow.
In order to cover this defect inherent to take-down bows, it has been proposed to provide the joint structure of a bow with a function to allow adjustment in angular position of a limb with respect to an associated handle riser in order to obtain optimum balance of force over the entire construction of the bow.
As later described in more detail, one conventional example of this sort employs a two point support for the limb. More specifically, a plug of the limb is received and held firmly in a socket of a handle riser by means of a pair of screw members providing the above-described two point support. This two point support tends to cause significant stress concentration on the screw members when the string is drawn for shooting, and repeated stress concentration causes breakage of the plug, thereby lowering durability of the bow. In addition, transverse holes have to be formed through walls of the socket in order to accommodate the screw members, and presence of such holes wields ill influence on the strength of the socket of the handle riser.
In order to cover this disadvantage, another conventional example of this sort includes a flat strap which is interposed between the plug of the limb and the screw member and dissipates the stress otherwise concentrating on the screw member. Use of such a strap for one of the two supports, however, causes change in the basis for calculation of strength distribution over the entire construction of the bow, thereby complicating correct mechanical designing of the bow construction.